CN103208937A - Single-phase photovoltaic grid-connected inverter - Google Patents

Single-phase photovoltaic grid-connected inverter Download PDF

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CN103208937A
CN103208937A CN2013100894724A CN201310089472A CN103208937A CN 103208937 A CN103208937 A CN 103208937A CN 2013100894724 A CN2013100894724 A CN 2013100894724A CN 201310089472 A CN201310089472 A CN 201310089472A CN 103208937 A CN103208937 A CN 103208937A
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voltage
circuit
output
inverter
transformer
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张淼
刘姝琳
陈思哲
唐雄民
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Guangdong University of Technology
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Guangdong University of Technology
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Abstract

The invention discloses a single-phase photovoltaic grid-connected inverter which mainly comprises a direct current/direct current (DC/DC) voltage converter, a direct current/alternating current (DC/AC) voltage converter, a current and voltage detecting circuit, a controller and a control circuit. The DC/DC part adopts a logic link control (LLC) resonance half bridge to finish conversion of direct current voltage, and a closed loop control circuit for outputting voltage is added, so that the DC/DC no longer outputs constant direct current voltage but the voltage with the steam-bread-shaped waveform and having the same frequency and phase with a power grid, and a resonance inductor and a resonance capacitor in the circuit are designed to effectively reduce switch loss and switch noises. In the DC/AC part, the voltage with the steamed-bread-shaped waveform serves as the input voltage to be connected with a direct current side of the inverter, so that effective inversion of the voltage is achieved, simultaneously voltage difference between two ends of a filter inductor in the inversion circuit is effectively reduced, the output current is smooth, and the harmonic content is reduced. The single-phase photovoltaic grid-connected inverter is small in size, high in efficiency, stable in performance, and easy to implement, and the harmonic content after the inversion is less, and the size of a harmonic suppression circuit is small.

Description

A kind of single-phase photovoltaic grid-connected inverter
Technical field
The present invention relates to single-phase photovoltaic grid-connected inverter field, more specifically, relate to a kind of single-phase photovoltaic grid-connected inverter.
Background technology
Growing along with social production, in continuous growth, the energy crisis in the global range also becomes increasingly conspicuous to the demand of the energy.Fossil energy in the earth is limited, can be consumed to the greatest extent one day.Along with the minimizing of fossil energy, its price also can improve, and this will seriously restrict the development of production and the raising of living standards of the people.Regenerative resource is to satisfy a kind of valuable source of world energy sources demand, and is particularly more important for our this populous nation.Wherein solar energy resources is very abundant in China, and its application has good prospect.
The core technology of grid-connected photovoltaic system is combining inverter, directly has influence on economy and the reliability of electricity generation system.Therefore the service behaviour that improves photovoltaic combining inverter becomes the focus of research in recent years.
About the research of single-phase photovoltaic grid-connected inverter, adopt traditional Boost circuit to carry out voltage transformation and power tracking usually in the DC/DC part at present, the sort circuit capacity usage ratio is on the low side, and design is complicated.Usually adopt the discrete component full-bridge inverter in DC/AC part, the sort circuit construction cycle is long, poor stability, and the direct voltage partly exported from DC/DC of the DC side of inverter reception, and the sinusoidal voltage harmonic content after the inversion is big.On control chip is selected, adopt dsp processor usually, expensive though the dsp processor performance is excellent, can increase the cost of combining inverter so greatly.
In sum, existing single-phase photovoltaic grid-connected inverter controller exists power utilization low, poor stability, and the construction cycle is long, cost height, shortcomings such as the sinusoidal voltage harmonic content height of exporting after the inversion.
Summary of the invention
Single-phase photovoltaic grid-connected inverter power utilizes the high deficiency of exporting after rate variance, poor stability and the inversion of sinusoidal voltage harmonic content in the prior art in order to overcome, the present invention proposes a kind of single-phase photovoltaic grid-connected inverter, single-phase photovoltaic grid-connected inverter of the present invention is when improving power utilization, strengthen its stability, and reduced the harmonic content of the output current that is incorporated into the power networks.
To achieve these goals, technical scheme of the present invention is:
A kind of single-phase photovoltaic grid-connected inverter mainly comprises DC/DC electric pressure converter, DC/AC voltage inverter, electric current and voltage detecting circuit and controller and control circuit; Photovoltaic cell inserts DC/DC electric pressure converter, the output termination DC/AC voltage inverter of DC/DC electric pressure converter; Electric current and voltage detecting circuit detect voltage, the electric current of DC/DC electric pressure converter output, output signal is transferred to controller and control circuit, electric current and voltage detecting circuit also detect the current delivery of DC/AC voltage inverter output to controller and control circuit, described controller and control circuit control DC/DC electric pressure converter, DC/AC voltage inverter;
Described DC/DC electric pressure converter contains that the voltage that is useful on photovoltaic cell output boosts and LLC resonance oscillation semi-bridge and the PWM of MPPT maximum power point tracking follow the tracks of the control hardware circuit; And be used for exporting and the output voltage closed control circuit of electrical network with the steamed bun shape voltage waveform of frequency, homophase.
The LLC resonance oscillation semi-bridge receives the direct voltage of photovoltaic cell output, and control and maximal power tracing boost.Partly adopt the reinforcement version integrated control chip of LLC and LLC resonant circuit to finish voltage transitions and maximal power tracing at DC/DC.The output voltage closed control circuit makes DC/DC partly export with electrical network with frequency and synchronous steamed bun shape voltage waveform.
Preferably, described LLC resonance half-bridge circuit comprises two switching device Q 1, Q 2, body diode-D ' 2And parasitic capacitance-C ' 2, the series resonance inductance L r, the series resonance capacitor C r, parallel resonant inductor L m, be with tapped transformer T, full-wave rectification diode D 1-D 2, outputting inductance L o, output capacitance C oWith load R o
Described switching device Q 1With body diode D ' 1, parasitic capacitance C ' 1Parallel connection is first parallel circuits, switching device Q 2With body diode D ' 2, be second parallel circuits, parasitic capacitance C ' 2Parallel connection, above-mentioned first and second parallel circuits series connection, an end of second parallel circuits is by the series resonance inductance L rConnect an end on the former limit of transformer T, the other end of second parallel circuits is by the series resonance capacitor C rConnect the other end on the former limit of transformer T, parallel resonant inductor L mConnect the two ends on the former limit of transformer T, the secondary one terminating diode D of transformer T 1Positive pole, diode D 1Negative pole meet output capacitance C respectively oWith load R oAn end, capacitor C oWith load R oThe secondary centre tap of another termination transformer T, diode D 1Negative pole also meet diode D 2Negative pole, diode D 2The other end of secondary of cathode connecting transformer T.
Preferably, described output voltage closed control circuit comprises voltage sensor, divider resistance and transport and placing device, described voltage sensor sampling line voltage is input to transport and placing device, the output voltage of described divider resistance sampling transformer T secondary is input to transport and placing device, the input of the output termination DC/DC electric pressure converter of transport and placing device;
The former secondary sampling optical coupling isolator of described transformer T is isolated.
Because feedback signal changes output (transformer secondary) from the DC/DC electric pressure converter, control signal is used for the former limit of transformer, and in order to guarantee the electromagnetic decoupling of the former secondary of transformer, former secondary is not altogether, so used light-coupled isolation, guaranteed control signal accurately and reliably.
Preferably, described DC/AC voltage inverter adopts the full bridge inverter of integrated power to realize the voltage inversion.The DC/AC voltage inverter receives DC/DC electric pressure converter output steamed bun wave voltage waveform, adopts full bridge inverter to realize the voltage inversion.The DC/AC voltage inverter adopts integrated power module to replace common discrete component full-bridge inverter, and on-chip system chip adopts timing ratio to finish PWM and follows the tracks of control simultaneously.
Preferably, described controller and control circuit sampling single-chip microcomputer is as controller.Adopt Single Chip Microcomputer (SCM) system to replace expensive dsp processor in the selection of control chip, finish circuit control, control is handled and followed the tracks of to signal.
Preferably, described electric current and voltage detecting circuit comprise voltage hall sensor, signal conditioning circuit, and the output of voltage hall sensor connects controller and control circuit by signal conditioning circuit.Because Chip Microcomputer A conversion sampled value can only be 0～VREF, and transducer output is the signal that positive negative value is subtracted each other, so before being connected to the AD sampling end, need signal conditioning circuit of design.Way in the design be sensor output signal and reference voltage signal through the in-phase adder stack, and amplify slightly or dwindle, make the range that reaches the AD conversion.This part function has amplifier to finish.
In the present invention, DC/DC partly adopts the LLC resonance oscillation semi-bridge, replaces traditional B oost circuit, realizes voltage transitions and maximal power tracing.Be the reduction of device volume, replace common discrete component full-bridge inverter in the DC/AC part with integrated power module, shorten the construction cycle simultaneously, and adopt timing ratio to finish PWM by on-chip system chip and follow the tracks of control.In addition, for the be incorporated into the power networks harmonic content of output current of reduction, propose to do input voltage with " steamed bun ripple " and replace traditional direct voltage to insert the DC side of inverter.For reaching this purpose, in the DC/DC circuit, added the Closed loop Control of output voltage, DC/DC is partly exported no longer be constant DC to be pressed, but with electrical network with frequently and synchronous steamed bun shape voltage waveform.
LLC resonance oscillation semi-bridge in the DC/DC part receives the direct voltage of solar panel output, boost control and MPPT maximum power point tracking, and electric current and voltage sampling circuit are obtained the pwm signal branch compare.DC/AC partly receives the frequently same and synchronous steamed bun shape voltage waveform with electrical network that DC/DC partly exports, and realizes the voltage inversion by full bridge inverter.
Compared with prior art, the invention has the advantages that:
1. partly adopt the LLC resonance oscillation semi-bridge at DC/DC, replace traditional Boost circuit, and constitute the LLC resonance oscillation semi-bridge by integrated control chip and auxiliary circuit, and adding output voltage Closed loop Control, make solar cell capacity usage ratio height, simplicity of design, stable performance.
2. partly adopt integrated power module to replace common discrete component-full-bridge inverter at DC/AC, make circuit stability good, and shorten the construction cycle greatly.
3. in the selection of control chip, abandon expensive dsp processor, adopt price material benefit and function single-chip microcomputer insolently, effectively reduce the development cost of combining inverter.
4. for reducing the harmonic content of the output current that is incorporated into the power networks, propose to do input voltage with the steamed bun ripple and replace traditional direct voltage to insert the DC side of inverter.For reaching this purpose, in the DC/DC circuit, added the voltage close loop control technology, making the DC/DC output no longer is that constant DC is pressed, but with electrical network with frequently and synchronous steamed bun shape voltage waveform.
Description of drawings
Fig. 1 is single-phase photovoltaic grid-connected inverter principle framework figure.
Fig. 2 is LLC controlled resonant converter schematic diagram.
Fig. 3 is for searching the curve chart of maximum power point by change on-state rate a.
Fig. 4 is full-bridge single-phase active inversion topological schematic diagram.
Fig. 5 is the inverter output current figure of direct voltage input.
The inverter output current of Fig. 6 steamed bun shape voltage input.
Embodiment
Below in conjunction with accompanying drawing the present invention is described further, but embodiments of the present invention are not limited to this.
The present invention is a kind of single-phase photovoltaic grid-connected inverter, and its theory diagram such as accompanying drawing 1 mainly comprise DC/DC electric pressure converter, DC/AC voltage inverter, electric current and voltage detecting, controller and control circuit.LLC resonance oscillation semi-bridge in the DC/DC part receives the direct voltage of photovoltaic cell output, finish boost control and MPPT maximum power point tracking, and obtain the pwm signal branch by electric current and voltage Hall sample circuit and compare, realize the closed-loop control of output voltage, output and the steamed bun shape voltage waveform of electrical network with frequency, homophase.Integrated power module in the DC/AC part receives DC/DC and partly exports the steamed bun wave voltage, finishes the voltage inversion, and adopts timing ratio PWM to finish and follow the tracks of control.
The present invention is a kind of single-phase photovoltaic grid-connected inverter, and the concrete implementation step of the implementation method of single-phase photovoltaic grid-connected inverter of the present invention is as follows
Global design thought according to system, the relatively independent work of DC/AC inverter of the front end DC/DC conversion of system and rear end, the former is responsible for boosting and controls and generate steamed bun shape waveform, and the latter is responsible for inversion and Current Control, and by controller the signal that adopts circuit to collect is coordinated control.
1.DC/DC voltage transformation part
(1) control of boosting
LLC resonance oscillation semi-bridge in the DC/DC part receives the direct voltage of solar panel output, the control of boosting.LLC resonance oscillation semi-bridge principle topology as shown in Figure 2.
From accompanying drawing 2 as can be known, LLC resonance oscillation semi-bridge topology element has: two switching device Q 1, Q 2, body diode D ' 1-D ' 2And parasitic capacitance C ' 1-C ' 2, the series resonance inductance L r(inductance value hour can be only by transformer leakage inductance L kRealization), series resonance capacitor C r, parallel resonant inductor L m(generally being realized by the static exciter inductance), band interphase reactor transformer T; Full-wave rectification diode D 1-D 2, outputting inductance L o, output capacitance C oWith load R o
Switching device Q wherein 1With body diode D ' 1, parasitic capacitance C ' 1Parallel connection is first parallel circuits, switching device Q 2With body diode D ' 2, be second parallel circuits, parasitic capacitance C ' 2Parallel connection, above-mentioned first and second parallel circuits series connection, an end of second parallel circuits is by the series resonance inductance L rConnect an end on the former limit of transformer T, the other end of second parallel circuits is by the series resonance capacitor C rConnect the other end on the former limit of transformer T, parallel resonant inductor L mConnect the two ends on the former limit of transformer T, the secondary one terminating diode D of transformer T 1Positive pole, diode D 1Negative pole meet output capacitance C respectively oWith load R oAn end, capacitor C oWith load R oThe secondary centre tap of another termination transformer T, diode D 1Negative pole also meet diode D 2Negative pole, diode D 2The other end of secondary of cathode connecting transformer T.
The soft on-off principle of LLC resonance oscillation semi-bridge mainly is Q 1And Q 2The no-voltage conducting, in certain section narrow frequency range, namely near fs, can accomplish Q 1And Q 2Zero-current switching.This novel circuit topology has bigger competitiveness aspect the loss of reduction switching device.Simultaneously can find out this asymmetric half-bridge circuit, transformer original edge voltage peak value is V In, the V of contrast symmetric form half-bridge circuit In/ 2, the space multiplication of boosting of transformer.At Q 1Under the situation of turn-offing, the dependence resonance that continues of electric current realizes that the symmetric form half-bridge then is to rely on mid-point voltage to realize that electric current continues, and the visible energy utilance is higher, and the volume of transformer of this topological circuit can dwindle.
The output voltage regulative mode of resonant circuit is based on frequency modulation, but not pulse width modulation, in order to satisfy the resonance requirement, upper and lower bridge arm conducting pulse duty factor is all a little less than 0.5.Because the LLC resonance topological is in conjunction with traditional series resonance and parallel resonance, its operating frequency is wideer with respect to traditional resonance topological, if with L r-C rResonance frequency be f r = 1 2 π L r · C r , With L r-L m-C rResonance frequency be f m = 1 2 π ( L r + L m ) · C r .
The series resonant switched frequency of tradition must be higher than resonance frequency, i.e. f〉f r, and the LLC controlled resonant converter can also work in f m＜f＜f rAnd f=f rAs seen two states, is main resonance topological based on frequency modulation, and the LLC controlled resonant converter has the pressure regulation advantage more.About LLC resonance oscillation semi-bridge parameter designing, the structural analysis according to the LLC resonance topological can draw LLC resonance frequency f〉f r, the maximum operating frequency of selected chip is 500kHz, with respect to the existence of circuit element parameter error, and the existence of electric capacity dead resistance, the operating frequency initial design values is decided to be 150-200kHz, to strengthen the debugging scope of later stage parameter optimization.By:
f r = 1 2 π L r · C r - - - ( 1 )
Can get, when choosing C rValue is during for common 0.1uF,
L r = 1 ( 2 πf ) 2 C r - - - ( 2 )
Can get L rValue is 11.26 μ H～6.33 μ H.
Yet also can be known by top topological analysis, as the leakage inductance L of transformer kWhen existing, and magnetizing inductance L m, the resonant operational frequency of circuit there is very big influence, these factors all can reduce the resonance frequency of circuit, and the leakage inductance of μ H level is common in actual applications, and the magnetizing inductance of switching mode power supply transformer also is μ H level, so L rGet smaller value, select 6.5 common μ H for use.Choosing of resonant capacitance and resonant inductance is decided to be: L r=6.5 μ H, C r=0.1 μ F.
(2) formation of steamed bun ripple
On the basis of LLC resonance oscillation semi-bridge, DC/DC partly adds the Closed loop Control of output voltage, thereby makes DC/DC partly export with electrical network with frequency and synchronous steamed bun shape voltage waveform.Use the amplifier chip to realize comparing function, by voltage sensor from electrical network sampled voltage signal as desired signal, and by divider resistance sampling and outputting voltage value.Because feedback signal changes output (transformer secondary) from DC/DC, control signal is used for the former limit of transformer, and in order to guarantee the electromagnetic decoupling of the former secondary of transformer, former secondary so used light-coupled isolation, guarantees control signal accurately and reliably not altogether.
(3) maximal power tracing
This method uses the increment conductance method to finish the maximal power tracing control of system.This method is by judgment task electric current I and maximum power point electric current I MaxBetween relation, the on-state rate a of switching device is controlled, increase or reduce the output current of battery, make the power stability of battery at maximum power point P MaxGo up or near, as accompanying drawing 3.
2.DC/AC voltage inversion part
Partly receive the frequently same and synchronous steamed bun shape voltage waveform with electrical network that DC/DC partly exports at DC/AC, and realize the voltage inversion by full bridge inverter.Adopt full bridge inverter in the design, its principle topology diagram as shown in Figure 4.
The topological structure of full-bridge single-phase active inversion as shown in Figure 4, its Topological component has: 4 switching device Q 3～Q 6, 4 sustained diode 3～D 6, energy storage inductor L ' rWith isolating transformer T '.In inverter circuit, switching device is main MOSFET or the IGBT of using at present, and the body diode of these two kinds of switching devices all can't satisfy more powerful afterflow requirement, all will be at switching device high performance fly-wheel diode in parallel under most of situation.Can pass through Q in the circuit 5And Q 6Break-make control sense of current, Q 3And Q 4Break-make control the size of electric current.Certainly arbitrary switching tube to upper and lower bridge arm can be controlled sense of current and size, as turn-offing Q 5Also can control size of current.Particularly under the high power contravariant state, can come the operating current of four fly-wheel diodes of average flowing-through by the change of symmetry, increase the working life of device.
In the design of inverter circuit, relate generally to the selection of bootstrap capacitor and the filter capacitor filter inductance of circuit.The selection of bootstrap capacitor size, the application experience that the bootstrap capacitor that the databook of selected power integration module provides is selected, very fast selected bootstrap capacitor is 2.2 μ F.The selection of filter capacitor filter inductance is according to the topological analysis to full-bridge inverting, as can be known:
Figure BDA00002938258600071
Wherein Δ t gets the control transformation step-length 50 μ s(20kHz of single-chip microcomputer), Δ I is 10% of load current, Δ U is that prime output voltage peak value and isolating transformer original edge voltage peak value are only poor.
L = ΔU · T ΔI = 36 × 50 × 10 6 3.6 × 10 % = 5 mH - - - ( 3 )
Withstand voltage is mainly considered in the selection of filter capacitor, and its capacitance is generally considered between the 1-10 μ F.
3. electric current and test section
For realizing the isolation voltage sampling, the closed loop voltage hall sensor is adopted in design, carries out voltage detecting.Because Chip Microcomputer A conversion sampled value can only be 0～V REF, and transducer output is the signal that positive negative value is subtracted each other, so before being connected to the AD sampling end, also need to design a signal conditioning circuit.Way be sensor output signal and reference voltage signal through the in-phase adder stack, and amplify slightly or dwindle, make the range that reaches the AD conversion.
4. control circuit and controller design
(1) control method introduction
What partly adopt in inversion is that PWM follows the tracks of the control method.This method as the reference signal, as feedback signal, provides the waveform of actual current the current waveform of expectation two kinds instantaneous value to compare, to determine the break-make of inverter circuit switching device, the variation of the output tracking desired signal of feasible reality.
(2) timing sampling program
For finishing the observing and controlling function of system, the instantaneous electrical value of the necessary timing sampling system of single-chip microcomputer is as feedback quantity.According to the requirement of timing ratio than the PWM tracking and controlling method, need a desired value and feedback to compare, so grid voltage waveform is desired value, the output current wave that is incorporated into the power networks is controlled volume, will be as feedback quantity, these two electric parameters are controlled so single-chip microcomputer will be sampled.
For improving control precision, determine to use 12 ADC of single-chip microcomputer to finish two signals sampling separately.(this single-chip microcomputer is inner integrated one 12 and 8 bit A/D converters, respectively have 8 sampling channels).The sampling of AD is overflowed triggering by timer 2, overflows after AD converts to trigger to interrupt, and carries out sampled value and handles.
Program leaves two unlike signals in the array in, the AD circulating sampling, and the array circulation is preserved.Single-chip microcomputer distributes sampling channel by changing AMX0SL channel register value.
(3) timing ratio is controlled than PWM
In inversion topological is analyzed, during the forward inversion, Q 3, Q 6Conducting, actual current amplitude be greater than expectation during amplitude, Q 3Close; Oppositely during inversion, Q 4, Q 5Conducting, actual current amplitude be greater than expectation during amplitude, Q 4Close.It more also is to adopt this method that PWM follows the tracks of,
Emulation explanation based on PSIM
(1) emulation between novelty application and the traditional circuit relatively
In grid-connected inverting system, grid-connected current must with line voltage with homophase frequently, the current harmonic content of inverter output must be lower than the certain standard value, otherwise will have influence on the normal operation of electrical network, and the generation of current harmonics, come from the process of dc inversion one-tenth interchange the existence of voltage difference between electrical network and the switching device.Though improve the harmonic content that the switching device switching frequency can reduce output current, but for the raising than the high power device switching frequency, present application is stuck on this bottleneck of 10-50kHz always, the reduction of output current harmonics content is the focus that development and Design person pays close attention to always, also relates to the key issue that photovoltaic DC-to-AC converter could large-scale application.This method proposes a kind of new application architecture, namely directly do not adopt dc inversion to become to exchange, and the steamed bun shape waveform after similar sinusoidal full-wave rectification of front-end structure of inverter circuit is called steamed bun shape waveform in the present invention.
Accompanying drawing 5 and 6 is under same switching frequency, respectively the inverter output voltage that obtains of input direct voltage and steamed bun voltage.By contrast as can be known, make output current seem more level and smooth, harmonic content reduces.This is can effectively reduce the voltage difference at filter inductance two ends in the inverter circuit during because of input steamed bun shape voltage.By more as can be known, this paper designs the way that the prime of employing is fed back in advance, and is with the obvious advantage.
Above-described embodiments of the present invention do not constitute the restriction to protection range of the present invention.Any modification of within spiritual principles of the present invention, having done, be equal to and replace and improvement etc., all should be included within the claim protection range of the present invention.

Claims (6)

1. a single-phase photovoltaic grid-connected inverter mainly comprises DC/DC electric pressure converter, DC/AC voltage inverter, electric current and voltage detecting circuit and controller and control circuit; Photovoltaic cell inserts DC/DC electric pressure converter, the output termination DC/AC voltage inverter of DC/DC electric pressure converter; Electric current and voltage detecting circuit detect voltage, the electric current of DC/DC electric pressure converter output, output signal is transferred to controller and control circuit, electric current and voltage detecting circuit also detect the current delivery of DC/AC voltage inverter output to controller and control circuit, described controller and control circuit control DC/DC electric pressure converter, DC/AC voltage inverter; It is characterized in that,
Described DC/DC electric pressure converter contains that the voltage that is useful on photovoltaic cell output boosts and LLC resonance oscillation semi-bridge and the PWM of MPPT maximum power point tracking follow the tracks of the control hardware circuit; And be used for exporting and the output voltage closed control circuit of electrical network with the steamed bun shape voltage waveform of frequency, homophase.
2. single-phase photovoltaic grid-connected inverter according to claim 1 is characterized in that, described LLC resonance half-bridge circuit comprises two switching device Q 1, Q 2, body diode-D ' 2And parasitic capacitance-C ' 2, the series resonance inductance L r, the series resonance capacitor C r, parallel resonant inductor L m, be with tapped transformer T, full-wave rectification diode D 1-D 2, outputting inductance L o, output capacitance C oWith load R o
Described switching device Q 1With body diode D ' 1, parasitic capacitance C ' 1Parallel connection is first parallel circuits, switching device Q 2With body diode D ' 2, be second parallel circuits, parasitic capacitance C ' 2Parallel connection, above-mentioned first and second parallel circuits series connection, an end of second parallel circuits is by the series resonance inductance L rConnect an end on the former limit of transformer T, the other end of second parallel circuits is by the series resonance capacitor C rConnect the other end on the former limit of transformer T, parallel resonant inductor L mConnect the two ends on the former limit of transformer T, the secondary one terminating diode D of transformer T 1Positive pole, diode D 1Negative pole meet output capacitance C respectively oWith load R oAn end, capacitor C oWith load R oThe secondary centre tap of another termination transformer T, diode D 1Negative pole also meet diode D 2Negative pole, diode D 2The other end of secondary of cathode connecting transformer T.
3. single-phase photovoltaic grid-connected inverter according to claim 1, it is characterized in that, described output voltage closed control circuit comprises voltage sensor, divider resistance and transport and placing device, described voltage sensor sampling line voltage is input to transport and placing device, the output voltage of described divider resistance sampling transformer T secondary is input to transport and placing device, the input of the output termination DC/DC electric pressure converter of transport and placing device;
The former secondary sampling optical coupling isolator of described transformer T is isolated.
4. according to described each the single-phase photovoltaic grid-connected inverter of claim 1-3, it is characterized in that described DC/AC voltage inverter adopts the full bridge inverter of integrated power to realize the voltage inversion.
5. single-phase photovoltaic grid-connected inverter according to claim 1 is characterized in that, described controller and control circuit sampling single-chip microcomputer are as controller.
6. single-phase photovoltaic grid-connected inverter according to claim 5, it is characterized in that, described electric current and voltage detecting circuit comprise voltage hall sensor, signal conditioning circuit, and the output of voltage hall sensor connects controller and control circuit by signal conditioning circuit.
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Application publication date: 20130717